1. Field of the Invention
The present invention relates to a pneumatic tire in which shapes of grooves formed in a middle portion are improved, thereby enhancing drainage performance while maintaining uneven wear resistance.
2. Description of the Background Art
A pneumatic tire of a block pattern in which a plurality of blocks is formed on a tread portion of the tire is known. In recent years, it is desired to further enhance drainage performance of the pneumatic tire. To enhance the drainage performance, it is necessary to smoothly discharge, toward a ground-contact end, a water film between the tread portion and a road surface, especially a water film near a tire equator. To smoothly discharge such a water film, it is known to increase a width and/or a depth of a groove in a middle portion which lies between the ground-contact end and the tire equator.
However, the above-described technique has a problem that since rigidity of the block is lowered, the uneven wear resistance is prone to be deteriorated. Enhancement of the drainage performance and securement of rigidity of the block are in an antinomic relation, and it is difficult to satisfy both of them. There is a related art as follows: